Various types of windshield wiper assemblies are currently available for motor vehicles. Of the type which extend through a windshield, it is common to support and position the wiper arm on a through-the-pane drive spindle which is attached to a motor fixed to the inside cab of the vehicle. In this design, it is necessary to provide a fixed and correctly positioned pivot for a control arm which lies parallel to the wiper arm. In order to ensure a correct position of the control arm relative to the drive spindle, one prior art patent (Switzerland 244,749) has suggested that the control arm supporting shaft also extends through the windshield. However, this solution is unattractive because two holes have to be formed in the windshield and this is both expensive and creates a region of weakness in the windshield.
For those patents which teach the use of a single drive spindle to control both the wiper arm and the control arm, see Great Britain Pat. No. 1,234,040 and U.S. Pat. No. 3,893,204, there is a problem in that torque arising during the operation of the wiper blade causes the drive spindle to bend and/or vibrate. When the drive spindle has a bushing around it which is snug against the outer circumference of the windshield, the vibration is directly transmitted to the windshield and this is undesirable. Also, the bending of the drive spindle can disrupt the oscillatory sweeps of the wiper blade. Still another solution to having only one hole formed in the windshield and still avoid the vibration problem is to mount the control arm on a bracket located on the outside of the windshield and to secure it to the windshield frame. However, with this design it is impossible to ensure a precise alignment between the position of the drive spindle which is mounted through the windshield from the inside and the control arm bracket which is mounted on the outside of the windshield. Any variations in the relative positions of the drive spindle to the control arm bracket affects the orientation of the wiper blade and/or the end positions of its oscillatory sweep of the windshield. By misaligning the wiper blade, the desired sweep surface may be unattainable.
Now an improved parallel arm windshield wiper assembly has been invented which resolves the drawbacks present in the prior art.